Vision-Based Deformation Monitoring and Risk Analysis of Adjacent High-Speed Railway Piers Under Full Construction Process of New Bridges

The extensive development of high-speed railway (HSR) networks often necessitates construction activities adjacent to operational lines. However, existing studies have mostly focused on the substructure construction phase, lacking systematic consideration of cumulative effects throughout the construction process. This study proposes an integrated framework for risk-informed monitoring throughout the full construction process. The framework integrates the Analytic Hierarchy Process (AHP), triangular fuzzy numbers, and fuzzy comprehensive evaluation to construct a quantitative risk assessment model, decomposing the construction process into hierarchical risk factors and quantifying the weights of each factor. Furthermore, a non-contact real-time monitoring system based on Digital Image Correlation (DIC) is designed and deployed, enabling high-frequency, high-precision three-dimensional pier deformation measurement. Applied to a new bridge crossing the Beijing–Shanghai HSR, the risk model identified pile cap and pier construction as the highest-risk stage (weight: 0.311). The DIC system, validated against total station measurements (relative error < 5%), recorded cumulative pier deformations across 31 construction stages, all remaining within the ±1.2 mm early warning threshold, thereby validating the proposed risk assessment model. The integrated AHP-Fuzzy and DIC framework provides a robust paradigm for proactive risk management, confirming that risk-informed monitoring ensures construction impacts on existing HSR infrastructure remain within safe limits.